OpenXenManager is a graphical interface to manage XenServer / Xen Cloud Platform (XCP) hosts through the network. OpenXenManager is an open-source multiplatform clone of XenCenter (Citrix).
The source code can now be found on GitHub using the homepage link below

Amanda is the most popular Backup and Archiving software that protects multiple machines running various versions of Linux, UNIX and Microsoft Windows operating systems. It supports tapes, disks, optical media and changers.

Meet#Web is flexible module-based web-solution for organizers of all sorts of meetings from local sessions to international conferences/workshops.
Available options are paper submission/review, tutorials, hotel reservation form, invoicing, visa appliance form.
Main features include web interface for setup/configuration, collaboration, export, statistics, file uploads, e-mail notifications.

jEdit Plugin Central is the primary online repository of plugins for the jEdit text editor. In conjunction with this repository, the integrated Plugin Manager allows jEdit users to install, upgrade, and remove plugins without leaving the editor.

itracker is a true open source issue tracking system. itracker is built using Java enterprise technology. itracker is a professional, easy to use, open, easy to integrate, fast, modular, customizable and scalable solution for all kinds of projects.